NTRK1 and breast cancer: Met, which is also spontaneously amplified in a subset of Brca1/Trp53 (Smolen et al., 2006) and lunatic fringe deleted (Xu et al., 2012) mouse mammary tumors, is a receptor tyrosine kinase for hepatocyte growth factor that regulates a variety of downstream signal transduction pathways, including MAPK and PI3K-AKT (Gastaldi et al., 2010).